“A pair of American B-52 bombers flew over a disputed island chain in the East China Sea” on Monday, according to The Wall Street Journal, “in a direct challenge to China and its establishment of an expanded air-defense zone.”

Citing “U.S. officials” as its sources, the Journal adds that Chinese authorities were not told in advance of the planes’ flights.

Several other news outlets, including The New York Times, are also reporting the news. NPR correspondents are working their sources.